Semiconductor device

ABSTRACT

A semiconductor device includes a wiring board that has a conductive pattern formed on at least one principal surface, and an IC chip that is mounted on the wiring board. The IC chip includes a plurality of electrodes to make conductor connection with the wiring board. The conductive pattern includes a lead line pattern and a heat dissipation pattern. The lead line pattern is connected with at least one of the plurality of electrodes through a conductor. The heat dissipation pattern is physically spaced from the IC chip and the lead line pattern and has a larger surface area than the lead line pattern. Further, the lead line pattern and the heat dissipation pattern are placed opposite to each other with a gap therebetween, and their opposite parts respectively have interdigitated shapes and are arranged with the respective interdigitated shapes engaging with each other with the gap therebetween.

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2009-166975, filed on Jul. 15, 2009, thedisclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a semiconductor device that includes awiring board and an integrated circuit (IC) chip mounted thereon and,particularly, to a heat dissipation structure in a semiconductor device.

2. Description of Related Art

The heat value of an IC chip such as a liquid crystal driver IC duringoperation is on the increase. The increase in the IC chip heat value isparticularly significant in a semiconductor device using a flexiblewiring board compared to a semiconductor device using a rigid wiringboard. Therefore, a heat dissipation structure in a semiconductor devicebecomes increasingly important.

A flexible wiring board has a structure in which a conductor layer suchas lines is formed on a flexible insulating film. For example, theconductor layer is formed by applying copper foil to a polyimide film,which is the insulating film. The flexible wiring board has a lower heatcapacity and a lower mechanical strength compared to the rigid wiringboard for its thin profile. It is thus generally difficult to mountheavy parts such as a heat sink on the flexible wiring board.

In order to deal with the heat issue when using a flexible wiring board,Japanese Unexamined Patent Application Publications Nos. 2007-158001 and2004-111996 disclose a heat dissipation structure of a tape carrierpackage (TCP), which is one type of a semiconductor device using aflexible wiring board. The TCP disclosed in Japanese Unexamined PatentApplication Publication No. 2007-158001 (JP 2007-158001 A) has thefollowing structure. Namely, an IC chip that has an electrode for heatdissipation separately from an electrode used for signal input/outputwith an external device is mounted on a flexible wiring board. Further,a heat dissipation conductive pattern that is physically isolated from asignal line pattern is formed on the surface of the flexible wiringboard. The heat dissipation electrode of the IC chip and the heatdissipation conductive pattern of the wiring board are connected througha conductor (gold bump, solder etc.). In this specification, connectionthrough a conductor such as gold bump or solder is referred to as“conductor connection”.

Japanese Unexamined Patent Application Publication No. 2004-111996 (JP2004-111996 A) also discloses a technique that forms a heat dissipationconductive pattern on the surface of a flexible wiring board for thepurpose of heat dissipation of an IC chip mounted on the flexible wiringboard. However, in JP 2004-111996 A, no electrodes of the IC chip andthe heat dissipation conductive pattern are connected. Specifically, JP2004-111996 A discloses a structure in which the IC chip and the heatdissipation conductive pattern are physically spaced (FIG. 3 in JP2004-111996 A) and a structure in which the IC chip and the heatdissipation conductive pattern are physically contacted (FIG. 6 in JP2004-111996 A). More specifically, FIGS. 3 and 6 of JP 2004-111996 Ashow structures in which no electrodes of the IC chip and the heatdissipation conductive pattern are in conductor connection and the heatdissipation conductive pattern is formed opposite to all over the lengthof the short side of the rectangular IC chip.

SUMMARY

As described above, the semiconductor device disclosed in JP 2007-158001A has the heat dissipation structure in which the heat dissipationconductive pattern that is formed on the flexible wiring board and theheat dissipation electrode of the IC chip are connected by a conductorwith a low heat resistance. The heat resistance between the IC chip andthe heat dissipation conductive pattern thereby decreases, which allowsimprovement in heat dissipation effect. However, there are many caseswhere conductor connection cannot be made between the electrode of theIC chip and the heat dissipation conductive pattern, such as whenterminals with different potentials are arranged irregularly in thevicinity of the IC chip or when there is a concern about electro-staticdischarge (ESD). For example, when the IC chip is a driver IC thatdrives a liquid crystal display panel, the driver IC can suffer damagefrom discharge when a charged human body comes into contact with theliquid crystal display panel. Because the heat dissipation conductivepattern generally has a large surface area to enhance the heatdissipation effect, conductor connection between the heat dissipationconductive pattern and the IC chip causes an increase in the probabilitythat the IC chip is damaged by ESD.

On the other hand, as described above, the heat dissipation structuresdisclosed in JP 2004-111996 A are structures in which conductorconnection is not made between the electrode of the IC chip and the heatdissipation conductive pattern. Specifically, FIGS. 3 and 6 of JP2004-111996 A show the structures in which the heat dissipationconductive pattern and the chip electrode are electrically insulated,and the heat dissipation conductive pattern is formed opposite to allover the length of one side of the rectangular chip. The structure hasan advantage that it can reliably avoid the damage of the IC chip byESD, and it is thus effective in the case where conductor connectioncannot be made between the electrode of the IC chip and the heatdissipation conductive pattern.

However, it is considered to be difficult in practice to adopt thestructure in which the IC chip and the heat dissipation conductivepattern are physically in contact without contact between the electrodeof the IC chip and the heat dissipation conductive pattern (FIG. 6 in JP2004-111996 A), which is one of the heat dissipation structuresdisclosed in JP 2004-111996 A. It is particularly difficult in aflip-chip package (face-down package) where the IC chip is mounted withthe surface on which a functional circuit and an electrode are formedfacing the wiring board. A large number of electrode pads are oftenarranged in the peripheral part of the IC chip, which is required todecrease in size, in terms of ensuring stable connection, and it isnormally difficult to make physical contact between the heat dissipationconductive pattern and the IC chip by avoiding contact with theelectrode.

On the other hand, regarding the structure in which the IC chip and theheat dissipation conductive pattern are physically spaced (FIG. 3 in JP2004-111996 A), which is the other one of the heat dissipationstructures disclosed in JP 2004-111996 A, the length of the interface atwhich the rectangular IC chip and the heat dissipation conductivepattern are placed opposite to each other is as short as the length ofthe short side of the IC chip. Thus, heat conduction from the IC chip tothe heat dissipation conductive pattern is not sufficient, which raisesthe IC chip temperature and thus causes an increase in the temperaturegradient near the IC chip.

As described above, the heat dissipation structures disclosed in JP2007-158001 A and JP 2004-111996 A have a problem that heat conductionfrom the IC chip to the heat dissipation conductive pattern is notsufficient when conductor connection cannot be made between theelectrode of the IC chip and the heat dissipation conductive pattern.

An exemplary aspect of the present invention is a semiconductor devicewhich includes a wiring board that has a conductive pattern formed on atleast one principal surface, and an IC chip that is mounted on thewiring board. The IC chip includes a plurality of electrodes to makeconductor connection with the wiring board.

The conductive pattern includes a lead line pattern and a heatdissipation pattern. The lead line pattern is connected with at leastone of the plurality of electrodes through a conductor. The heatdissipation pattern is physically spaced from each of the IC chip andthe lead line pattern and has a larger surface area than the lead linepattern.

Further, the lead line pattern and the heat dissipation pattern areplaced opposite to each other with a gap therebetween, and oppositeparts of the lead line pattern and the heat dissipation patternrespectively have interdigitated shapes and are arranged with therespective interdigitated shapes engaging with each other with the gaptherebetween.

According to the exemplary aspect of the present invention describedabove, it is possible to efficiently release heat from the IC chip bythe conductive lead line pattern that is in conductor connection withthe electrode of the IC chip. Further, because the lead line pattern andthe heat dissipation pattern are arranged in such a way that theirinterdigitated shapes engage with each other with a gap therebetween, itis possible to make the total extension of the gap long enough andreduce the heat resistance between the lead line pattern and the heatdissipation pattern. It is thereby possible to reduce the heatresistance from the IC chip to the heat dissipation pattern, therebyenhancing the heat dissipation effect. Further, it is easy to make thetotal extension of the longitudinal length of the gap longer than thelength of the short side of the IC chip.

According to the exemplary aspect of the present invention describedabove, even when conductor connection cannot be made between theelectrode of the IC chip and the heat dissipation pattern, it ispossible to reduce the heat resistance between the IC chip and the heatdissipation conductive pattern and enhance the heat dissipation effect.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other exemplary aspects, advantages and features will bemore apparent from the following description of certain exemplaryembodiments taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a plan view schematically showing the structure of asemiconductor device according to a first exemplary embodiment of theinvention;

FIG. 2 is a plan view schematically showing an example of electrodelayout of an IC chip included in the semiconductor device shown in FIG.1;

FIG. 3 is an enlarged plan view showing the vicinity of a lead linepattern and a heat dissipation pattern included in the semiconductordevice shown in FIG. 1;

FIG. 4 is a schematic cross-sectional view along line A-A in FIG. 3;

FIGS. 5A and 5B are a plan view and a temperature distribution graph ofa semiconductor device to describe the heat dissipation effect of thesemiconductor device shown in FIG. 1;

FIGS. 5C and 5D are a plan view and a temperature distribution graph ofa semiconductor device according to a comparative example;

FIG. 6 is a view showing an alternative example of a lead line patternand a heat dissipation pattern;

FIGS. 7A to 7D are views showing alternative examples of a lead linepattern and a heat dissipation pattern;

FIGS. 8A to 8E are views showing alternative examples of a lead linepattern and a heat dissipation pattern;

FIGS. 9A and 9B are views showing alternative examples of a lead linepattern and a heat dissipation pattern;

FIGS. 10A and 10B are views showing alternative examples of a lead linepattern and a heat dissipation pattern;

FIGS. 11A and 11B are views showing alternative examples of a lead linepattern and a heat dissipation pattern;

FIG. 12 is a plan view schematically showing the structure of asemiconductor device according to a second exemplary embodiment of theinvention; and

FIG. 13 is an enlarged plan view showing the vicinity of a lead linepattern and a heat dissipation pattern included in the semiconductordevice shown in FIG. 12.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the appended drawings. Note that,in the appended drawings, structural elements that have substantiallythe same function and structure are denoted with the same referencenumerals, and repeated explanation of these structural elements isomitted.

First Exemplary Embodiment

A semiconductor device according to this exemplary embodiment is a tapecarrier package (TCP) and, specifically, a TCP that incorporates adriver IC for driving a liquid crystal display panel. FIG. 1 is aschematic plan view of a TCP 1 according to the exemplary embodiment.The TCP 1 includes a flexible wiring board 10 and an IC chip 11. Thewiring board 10 has a structure in which a conductive pattern is formedby copper foil or the like on a flexible insulating film such as apolyimide film. The conductive pattern includes an input signal linepattern 12, an output signal line pattern 13, a lead line pattern 14 anda heat dissipation pattern 15. Note that a plurality of sprocket holes100 made at regular intervals along both ends of the flexible wiringboard 10 are used for carrying and positioning of a carrier tape beforethe TCP 1 is cut out.

The IC chip 11 is flip-chip mounted on the principal surface of theflexible wiring board 10 where the conductive pattern is formed. The ICchip 11 has a plurality of first electrodes 111 that are used forinputting and outputting power supply, display data, control signals orthe like to and from an external device (e.g. a display controller onthe input side, a liquid crystal display panel on the output side etc.)and a plurality of second electrodes 112 that are usually not connectedwith an external device and principally used for the purpose of ensuringstable connection and dissipating heat.

FIG. 2 is a plan view showing an example of layout of the electrodes 111and 112 formed on the principal surface of the IC chip 11. In theexample of FIG. 2, the plurality of first electrodes 111 are arrangedalong the long side of the rectangular principal surface of the IC chip11, and the plurality of second electrodes 112 are arranged along theshort side of the principal surface of the IC chip 11. Each of theplurality of first electrodes 111 is joined to the input signal linepattern 12 or the output signal line pattern 13 by a conductor bump (Aubump, solder bump etc.). Further, each of the plurality of secondelectrodes 112 is joined to the lead line pattern 14 by a conductorbump. Note that the arrangement is just an example, and the secondelectrodes 112 are not necessarily arranged along the short side onlybut may be arranged along the long side or arranged along the bothsides.

Referring back to FIG. 1, the input signal line pattern 12 and theoutput signal line pattern 13 are used for inputting and outputtingpower supply, display data, control signals or the like between the ICchip 11 and an external device (e.g. a display controller on the inputside, a liquid crystal display panel on the output side etc.). Althoughnot shown in FIG. 1, the input signal line pattern 12 includes aplurality of fine input lines, and the output signal line pattern 13includes a plurality of fine output lines.

The lead line pattern 14 is in conductor connection with at least oneelectrode of the first electrodes 111 and the second electrodes 112. Theheat dissipation pattern 15 is physically spaced from each of the ICchip 11, the signal line patterns 12 and 13 and the lead line pattern14, and it has a larger surface area than the lead line pattern 14.Further, the lead line pattern 14 and the heat dissipation pattern 15are placed opposite to each other with a gap therebetween. Therespective parts of the lead line pattern 14 and the heat dissipationpattern 15 which are opposite to each other have an interdigitatedshape, and they are arranged in such a way that the respectiveinterdigitated shapes engage with each other with a gap therebetween. Inother words, the boundary line of the opposite parts of the lead linepattern 14 and the heat dissipation pattern 15 has an interdigitatedshape. The shape of the boundary line may be also regarded as acorrugated, zigzag, meandering or star-like shape.

FIG. 3 is an enlarged plan view showing the vicinity of the lead linepattern 14 and the heat dissipation pattern 15 located on the right sideof the IC chip 11 shown in FIG. 1. In the example of FIG. 3, the leadline pattern 14 is made up of five lead lines 141 to 145 that areseparated from one another. FIG. 4 is a schematic cross-sectional viewalong line A-A in FIG. 3. In FIG. 4, sealing resin is not shown. Asshown in FIG. 4, the lead line 145 is formed on a flexible insulatingfilm 101 and joined to the electrode 112 by a conductor bump 113. Theother lead lines 141 to 144 are also joined to the IC chip 11 by theconductor bump 113 in the same manner as the lead line 145.

Further, as shown in FIG. 3, the lead lines 141 to 145 are arranged toradiate out from the short side of the IC chip 11. The radial end partsof the lead lines 141 to 145 correspond to projecting parts of the leadline pattern 14. Further, the heat dissipation pattern 15 is arranged tosurround the end parts of the lead lines 141 to 145 with a gap 16therebetween. In other words, the lead lines 141 to 145 are arranged tocome inside the heat dissipation pattern 15. Specifically, projectingparts 151 to 156 of the heat dissipation pattern 15 extend between therespective lead lines 141 to 145, between the chip 11 and the line 141and between the chip 11 and the line 145.

In this manner, the opposite parts of the lead line pattern 14 (the leadlines 141 to 145) and the heat dissipation pattern 15 are designed withan interdigitated structure and arranged to engage with each other withthe gap 16 therebetween, thereby increasing the length of the oppositeparts of the pattern 14 and the pattern 15 (i.e. the length of theboundary line or the length of the gap 16). Because the gap 16, which isthe insulating film, has a lower heat conductivity than the patterns 14and 15 made of a conductor such as copper or aluminum, it causes anincrease in heat resistance at the boundary between the patterns 14 and15. However, by making the total extension of the longitudinal length ofthe gap 16 long enough, it is possible to reduce the heat resistancebetween the lead line pattern 14 and the heat dissipation pattern 15.Note that it is easy to make the total extension of the longitudinallength of the gap 16 longer than the length of the short side of the ICchip 11. Thus, when conductor connection cannot be made between the ICchip 11 and the heat dissipation pattern 15, the higher heat dissipationeffect can be expected in the heat dissipation structure according tothe exemplary embodiment compared to the heat dissipation structuredisclosed in JP 2004-111996 A (the structure in which the length of theinterface between the IC chip and the heat dissipation conductivepattern is about the length of the short side of the IC chip).

Hereinafter, the heat dissipation effect that is obtained by the layoutof the lead line pattern 14 and the heat dissipation pattern 15described in the exemplary embodiment is described with reference toFIGS. 5A to 5D. FIG. 5A is a plan view where isothermal lines L1 to L8are added to the layout of the patterns 14 and 15 shown in FIG. 3. FIG.5B is a graph showing a temperature distribution along the X-axis ofFIG. 5A. On the other hand, FIG. 5C is a plan view related to acomparative example in the case where the boundary line between thepatterns 14 and 15 does not have an interdigitated shape. FIG. 5D is agraph showing a temperature distribution along the X-axis of FIG. 5C. Itshould be noted that the structure shown in FIG. 5C is designed by theinventor of the present invention for the purpose of comparison with theTCP 1 and it is thus not a publicly known structure.

As is obvious from comparison between FIGS. 5B and 5D, according to theexemplary embodiment, heat is efficiently released from the IC chip 11to the heat dissipation pattern 15, so that the temperature of the ICchip 11 falls and the temperature of the heat dissipation pattern 15rises. The temperature gradient along the boundary P1 of the IC chip 11thereby becomes less steep as shown in FIG. 5B.

Because the temperature gradient near the IC chip 11, which is a heatsource, is steep in FIGS. 5C and 5D, reducing the temperature gradientleads to efficient heat dissipation. By forming the lead line pattern 14so as to radically spread out from the IC chip 11 as shown in FIGS. 1and 3, it is possible to improve the heat dissipation effect. This isbecause the radial line layout is along the diffusion direction of heatcurrent. By placing the radial lead line pattern 14 along the heatcurrent diffusion direction in close proximity to the IC chip 11, thetemperature gradient near the IC chip 11 becomes less steep as shown inFIGS. 5A and 5B, which allows efficient heat dissipation.

Further, with use of the radial lead line pattern 14, the total area ofthe lead line pattern 14 can be small. Therefore, the radial lead linepattern 14 is particularly effective when there is a concern aboutbreakdown of the IC chip 11 due to ESD.

According to the exemplary embodiment, even when conductor connection ofthe heat dissipation pattern 15 to the IC chip 11 is unavailable for thecountermeasure to ESD, the constraints on the electrode layout of the ICchip 11 or the like, it is possible to reduce the heat resistancebetween the IC chip 11 and the heat dissipation pattern 15 and increasethe heat dissipation effect. Further, by making the total extension ofthe gap 16 long enough, it is possible to obtain the heat dissipationeffect which is equal to when making conductor connection between the ICchip 11 and the heat dissipation pattern 15.

Noted that the shape of the lead line pattern 14 shown in FIGS. 1, 3 and5 is just an example. For example, when an electrical connection can bemade, the lead line pattern 14 may have an integral conductive patternin which the lead lines 141 to 145 are connected at a center part 146 asshown in FIG. 6.

Alternative examples of the lead line pattern 14 are shown in FIGS. 7Ato 7D and FIGS. 8A to 8E. FIGS. 7A to 7D show alternative examples ofthe lead line pattern 14 having the radial lead lines 141 to 145. FIG.7A is an example in which each of the lead lines 141 to 145 shown inFIG. 3 branches off to thereby further increase the boundary length.FIG. 7B is an example in which each of the lead lines 141 to 145 becomeswider toward their ends. FIGS. 7C and 7D are examples in which the endof each of the lead lines 141 to 145 is wider than the root and each hasa corrugated rim to thereby further increase the boundary length.

FIGS. 8A to 8E show alternative examples of the lead line pattern 14having the non-radial lead lines 141 to 145. Although the non-radiallead line pattern 14 is likely to be less advantageous than the radialpattern in terms of heat current diffusion characteristics, it iseffective when it is difficult to adopt the radial lead line pattern 14due to layout constraints.

Further, the heat dissipation pattern 15 may be electrically floating orprovided with a certain potential. For example, the heat dissipationpattern 15 may be grounded. In the heat dissipation structure accordingto the exemplary embodiment, the lead line pattern 14 and the heatdissipation pattern 15 are physically spaced from each other. Therefore,the heat dissipation structure is applicable also when a given potentialis provided to the heat dissipation pattern 15.

Furthermore, the electrodes 112 for heat dissipation may be connected toa power supply potential, a ground potential or the like inside the ICchip 11. Stated differently, the lead line pattern 14 (the lead lines141 to 145) may be electrically connected to an external device throughan internal line of the IC chip 11. In the heat dissipation structureaccording to the exemplary embodiment, the respective lead lines 141 to145 of the lead line pattern 14, and the lead line pattern 14 and theheat dissipation pattern 15 are respectively physically spaced from eachother. Therefore, the heat dissipation structure is applicable also whena given potential is supplied to the respective lead lines 141 to 145 ofthe lead line pattern 14.

Although the case where the heat dissipation pattern 15 is one islandpattern is described above, the heat dissipation pattern 15 may bedivided into a plurality of island patterns.

One feature of the heat dissipation structure according to the exemplaryembodiment is that the boundary line between the lead line pattern 14and the heat dissipation pattern 15 has an interdigitated shape(including a corrugated, zigzag, meandering or star-like shape). Thelayout is generally applicable to the part where the lead line pattern14 and the heat dissipation pattern 15 are arranged in close proximityto each other.

Specifically, it is more preferable that the boundary line (L22) betweenthe lead line pattern 14 and the heat dissipation pattern 15 opposite toeach other with a gap therebetween has an interdigitated shape as shownin FIG. 9B, compared to that the boundary line (L21) between thepatterns 14 and 15 is a straight line as shown in FIG. 9A. Further, whenthe lead line pattern 14 includes a plurality of fine lines (FIG. 10A),it is preferred to vary the lengths of the respective fine lines andmake a comb shape, so that the boundary line (L22) between the patterns14 and 15 has an interdigitated shape (FIG. 10B). Furthermore, when thelead line pattern 14 and the heat dissipation pattern 15 both include aplurality of fine lines, it is preferred to make the respective patternshave a comb shape and engage with each other with a gap therebetween, sothat the boundary line (L22) between the patterns 14 and 15 has aninterdigitated shape (FIG. 11B).

Second Exemplary Embodiment

In this exemplary embodiment, applications of the conductive patternlayout shown in FIGS. 9B, 10B and 11B are described. FIG. 12 is aschematic plan view of a TCP 2 according to the exemplary embodiment. Inthe example of FIG. 12, dummy lines (dummy leads) are formed in an area21 where the signal input/output patterns 13 and 14 are not formed. Itis generally practiced in a semiconductor device such as a TCP using aflexible wiring board to form dummy lines in an open part. The dummylines contribute also to the heat dissipation of the IC chip 11.

Further, in the example of FIG. 12, a folded line 24 is formed in thearea 21. The folded line 24 connects between the two electrodes 112which are not connected to an external device among the electrodes ofthe IC chip 11 in a folded fashion. The folded line 24 is placed forpower supply, for example. When the folded line 24 exists, the dummylines are divided by the folded line 24. In this exemplary embodiment,the layout of the conductive pattern shown in FIGS. 9 to 11 is used forimproving the heat conductivity between the divided dummy lines and thefolded line 24.

FIG. 13 is an enlarged plan view showing the vicinity of the folded line24 placed in the area 21. The folded line 24 is not connected to anexternal device and in conductor connection to the electrode 112 of theIC chip 11. Thus, the folded line 24 corresponds to the lead linepattern 14. Further, dummy lines 25 are physically spaced from each ofthe IC chip 11, the signal line patterns 12 and 13 and the folded line24 (which corresponds to the lead line pattern 14), and it has a largersurface area than the folded line 24. Thus, the dummy lines 25correspond to the heat dissipation pattern 15. Dummy lines 26 areconnected to a dummy electrode of the IC chip 11 through a conductorbump to ensure stable connection with the flexible wiring board 10. Notethat the dummy lines 26 are not necessarily in conductor connection tothe electrode of the IC chip 11.

As shown in FIG. 13, the opposite parts of the folded line 24 (whichcorresponds to the lead line pattern 14) and the dummy lines 25 (whichcorrespond to the heat dissipation pattern 15) have an interdigitatedshape and engage with each other with a gap therebetween, therebyreducing heat resistance. Likewise, it is preferred that the boundaryline between the dummy lines 26 and the folded line 24 on the IC chip 11side also has an interdigitated shape. It is thereby possible to reducethe heat resistance from the IC chip 11 to the dummy lines 25.

In the first and second exemplary embodiments of the present invention,the structure in which the lead line pattern is in conductor connectionwith the electrodes 112 which are placed separately from the electrodes111 being connected to an external device and principally used for thepurpose of ensuring stable connection and dissipating heat without beingconnected to an external device is described. However, at least one ofthe input signal line pattern 12 and the output signal line pattern 13which are connected to the electrodes 111 being connected to an externaldevice may be placed opposite to the heat dissipation pattern 15 with agap therebetween. In other words, at least one of the input signal linepattern 12 and the output signal line pattern 13 may serve also as thelead line pattern.

As described above, in the TCP 1 and the TCP 2, the lead line pattern 14and the heat dissipation pattern 15 are arranged to engage with eachother with a gap therebetween, and it is thus possible to reduce heatresistance without making electrical connection between the lead linepattern 14 and the heat dissipation pattern 15. Thus, the input signalline pattern 12 and the output signal line pattern 13 which should avoidelectrical connection with the heat dissipation pattern 15 may be usedas the lead line pattern 14. In this manner, because the signal linepatterns 12 and 13 or the like that are connected to an external devicecan be used as the lead line pattern 14, the heat dissipation structurewith the lead line pattern 14 and the heat dissipation pattern 15 has anadvantage of less constraints on layout.

Further, the heat dissipation structure of the semiconductor devicedescribed in the above first and second exemplary embodiments of thepresent invention is especially effective in a semiconductor deviceusing a flexible wiring board, particularly in a TCP having a structurein which a conductive layer formed on an insulating film is a singlelayer and an IC chip is flip-chip mounted on the same principal surfaceas the conductive layer. This packaging is called chip on film (COF). Inthe COF, there is no need to make a hole in a part of the insulatingfilm opposite to the IC chip and there is no need to use a flying lead.The COF in which the conductive layer is formed only on the principalsurface of the film and the IC chip is mounted on the principal surfaceis a generally used package type for its compatibility with a fine pitchstructure and its ability to reduce the manufacturing cost of the TCPand ensure the flexibility. On the other hand, in the TCP having such astructure, severe layout constraints are imposed on the conductivepattern, and the IC chip temperature is likely to rise. However, byusing the heat dissipation structure described in the first and secondexemplary embodiments, it is possible to enhance the heat dissipationeffect when conductor connection cannot be made between the IC chip 11and the heat dissipation pattern 15.

However, the heat dissipation structure of the semiconductor devicedescribed in the first and second exemplary embodiments is alsoapplicable to a semiconductor device that uses a flexible wiring boarddifferent from a TCP. Further, a wiring layer (conductive layer) of aflexible wiring board may have a multi-layer structure. Furthermore, aconductive layer may be formed on both principal surfaces of a flexiblewiring board. In addition, mounting of the IC chip 11 into the flexiblewiring board 10 is not limited to the flip-chip mounting describedabove. For example, it is applicable to tape automated bonding (TAB)mounting. Further, the heat dissipation structure is also applicable toa semiconductor device that uses a rigid wiring board, not limited to aflexible wiring board.

The first and second exemplary embodiments can be combined as desirableby one of ordinary skill in the art.

While the invention has been described in terms of several exemplaryembodiments, those skilled in the art will recognize that the inventioncan be practiced with various modifications within the spirit and scopeof the appended claims and the invention is not limited to the examplesdescribed above.

Further, the scope of the claims is not limited by the exemplaryembodiments described above.

Furthermore, it is noted that, Applicant's intent is to encompassequivalents of all claim elements, even if amended later duringprosecution.

1. A semiconductor device comprising: a wiring board that has aconductive pattern formed on at least one principal surface; and anintegrated circuit chip that is mounted on the wiring board and includesa plurality of electrodes to make conductor connection with the wiringboard, wherein the conductive pattern includes: a lead line pattern thatis connected with at least one of the plurality of electrodes through aconductor; and a heat dissipation pattern that is physically spaced fromeach of the integrated circuit chip and the lead line pattern and has alarger surface area than the lead line pattern, the lead line patternand the heat dissipation pattern are placed opposite to each other witha gap therebetween, and opposite parts of the lead line pattern and theheat dissipation pattern respectively have interdigitated shapes and arearranged with the respective interdigitated shapes engaging with eachother with the gap therebetween.
 2. The semiconductor device accordingto claim 1, wherein the lead line pattern is formed to radiate out fromthe integrated circuit chip, and the heat dissipation pattern is formedto surround radial end parts of the lead line pattern.
 3. Thesemiconductor device according to claim 1, wherein a principal surfaceof the integrated circuit chip has a rectangular shape, and a length ofthe opposite parts of the lead line pattern and the heat dissipationpattern is longer than a length of a short side of the integratedcircuit chip.
 4. The semiconductor device according to claim 1, whereinthe lead line pattern includes a plurality of lead lines connected withat least two of the plurality of electrodes.
 5. The semiconductor deviceaccording to claim 4, wherein the plurality of lead lines are formed toradiate out from the integrated circuit chip, and the heat dissipationpattern is formed to surround each end part of the plurality of radiallead lines.
 6. The semiconductor device according to claim 1, whereinthe lead line pattern includes a folded line pattern that connectsbetween two electrodes included in the plurality of electrodes.
 7. Thesemiconductor device according to claim 6, wherein the plurality ofelectrodes include another, electrode placed between the two electrodesconnected by the folded line pattern, the conductive pattern furtherincludes a dummy line pattern connected with said another electrodethrough a conductor, at least part of an edge of the folded line patternhas an interdigitated shape, and an end part of the dummy line patternon a side not connected with said another electrode has aninterdigitated shape and is arranged to engage with the interdigitatedshape of the folded line pattern with a gap therebetween.
 8. Thesemiconductor device according to claim 1, wherein the heat dissipationpattern includes a plurality of island patterns.
 9. The semiconductordevice according to claim 1, wherein the opposite parts of the lead linepattern and the heat dissipation pattern are made of an identicalconductive layer.
 10. The semiconductor device according to claim 1,wherein the conductive pattern is formed on one principal surface of thewiring board, and the integrated circuit chip is packaged on said oneprincipal surface of the wiring board on which the conductive pattern isformed.
 11. The semiconductor device according to claim 1, wherein thewiring board has a structure where the conductive pattern is formed by asingle conductive layer on a flexible film substrate.
 12. Thesemiconductor device according to claim 1, wherein the wiring board is aflexible wiring board.
 13. The semiconductor device according to claim1, wherein the semiconductor device is a tape carrier package.